Wireless home nets need 802.11a

The market for home networking is developing at a phenomenal rate. Service providers from the cable TV, telephony and digital subscriber line markets are vying to deliver bundled services such as basic telephone service, Internet access and entertainment directly to the consumer. What is needed is a cost-effective, robust, high-performance local-area network technology for distributing this multimedia information within the home. The benefits of using wireless connection instead of a phone line or power line are clear; wireless is the ultimate solution for portability and convenience. To many, this has been described as the holy grail of home networking: a true high-performance solution capable of meeting the existing and future needs of consumer multimedia networks at a competitive price.

To date, wireless networking solutions for the home are somewhat expensive and at best mediocre in terms of performance. Currently, a number of networking schemes are vying for the home market, including Bluetooth, HomeRF and the IEEE 802.11b standard.

Bluetooth has been generating a lot of interest for the home market, but it is principally a point-to-point wireless technology for transmission over very short distances. In essence, Bluetooth is an RF alternative to infrared. Bluetooth was designed for extremely low-cost, short-distance, low-bandwidth applications and is not a true LAN technology. Developed in 1998, it uses 2.4-GHz frequency-hopping spread-spectrum technologies to establish radio links for personal-area networks (PANs). Currently being adopted as the initial IEEE 802.15 standard, the Bluetooth format has an operating range limited to about 30 feet and can achieve data rates of only 1 Mbit/second. But it is the ideal solution for users who want to link portable devices such as cellular phones to personal digital assistants.

HomeRF is an amalgamation of the IEEE 802.11 standard and Digital European Cordless Telephony (DECT). The intent was to create a data and voice standard that would address the cost limitations of the consumer market. HomeRF also employs spread-spectrum radio technology and operates within the 2.4-GHz spectrum. While HomeRF currently transfers data at rates of around 1 to 2 Mbits/s, proposed legislation by the Federal Communications Commission could effectively raise those rates to 10 Mbits/s. With the first products just starting to ship, it is a lower cost solution, but it is too little, too late in terms of performance.

There are also products being developed to support the IEEE 802.11b wireless standard, which uses 2.4-GHz direct-sequence spread-spectrum technology. This standard can achieve data rates up to 11 Mbits/s, and there are proposals to extend it to 22 Mbits/s. While 802.11b represents a significant step in the right direction in terms of both performance and cost, it still falls short of the performance needs of a true multimedia LAN for the home. In addition, its use of the 2.4-GHz frequency band means it has to coexist with other devices, such as digital cordless telephones and microwave ovens.

Of the three primary connectivity standards, not one can achieve data rates higher than 11 Mbits/s, which just isn't enough to meet the demands of the home market. A home environment can be very complex, and to operate transparently the network has to have the capacity to handle multiple high-bandwidth tasks simultaneously. In a single home, a probable scenario has Mom and Dad watching DVD, a pay-per-view movie or digital TV program on one television (at 6 to 20-Mbits/s, depending on the format, i.e. streaming video, digital TV or HDTV); one of the kids watching another movie or TV on another set (at 6 to 20 Mbits/s); and another child or two surfing the Web, downloading MP3 files and the like (at 2 Mbits/s). That scenario alone would require in excess of 22 Mbits/s on a home network.

One of the major challenges to the proliferation of such formats as HDTV (20 to 40 Mbits/s) is the inability to deliver even one channel from a set-top box to an HDTV unit. Wireless again is the preferred media, given the flexibility of letting the set-top box with the broadband cable modem connection exist remotely from the HDTV unit. And we must not forget the other applications that may exist on home networks in the future, such as voice-over-Internet Protocol cordless telephones, security systems and other Internet-enabled appliances. Scalable network capacity is a key criterion for future services.

What the industry needs today is a standard that can address the performance requirements of the home market. The most promising solution is the IEEE 802.11a standard, which operates at the 5-GHz UNII (unlicensed National Information Infrastructure) band and can achieve data rates as high as 54 Mbits/s-a significant improvement over other standards-based wireless technology. The 802.11a standard has some unique and distinct advantages over other wireless standards in that it uses a relatively new technology called orthogonal frequency-division multiplexing (OFDM) as opposed to spread spectrum, and it operates in a clean band of frequencies at 5 GHz.

OFDM is a technology that resolves many of the problems associated with the indoor wireless environment. Indoor environments such as homes and offices are difficult because the radio system has to deal with a phenomenon called "multipath." Multipath is the effect of multiple received radio signals coming from reflections off walls, ceilings, floors, furniture, people and other objects. In addition, the radio has to deal with another frequency phenomenon called "fading," where blockage of the signal occurs due to objects or the position of a device relative to the Internet gateway.

OFDM has been designed to deal with these phenomena and at the same time utilize spectrum more efficiently than spread spectrum to significantly increase performance. Ratified in 1999, the IEEE 802.11a standard significantly increases the performance (54 Mbits/s vs.11 Mbits/s) of indoor wireless networks. At the same time, it creates a more robust communications link by using OFDM technology and moving to 5 GHz.

Tight embrace

So why hasn't IEEE 802.11a been embraced by OEM communications and multimedia vendors? There are two fundamental reasons. First, vendors have feared that 802.11a chip set solutions would not be available for another one to two years. Second, the market perceives that higher-frequency and more-complex technologies like OFDM are significantly more expensive. Higher-frequency radio technologies have historically required exotic, expensive semiconductor processes such as gallium arsenide, silicon on insulator and silicon germanium. The technical challenge before the industry is to implement 802.11a functionality completely in CMOS. We can then ultimately achieve single-chip implementations and utilize the world's lowest-cost and highest-volume semiconductor technology.

In fact, the market can expect to see a high-volume, low-cost CMOS "wireless engine" chip set that supports the 802.11a standard by the end of the current calendar year from Radiata. This will enable OEMs of residential Internet gateways and appliances as well as enterprise wireless LANs to provide 54 Mbits/s of wireless LAN connectivity at prices similar to existing 11-Mbit/s technology.

CHRIS FISHER IS VICE PRESIDENT OF SALES AND MARKETING AT RADIATA COMMUNICATIONS INC. (SAN JOSE, CALIF.).